Octal: Pertaining to a base 8 number system.

Offset: The difference in temperature between the set point and the actual process temperature. Also, referred to as droop.

Ohmeter: An instrument used to measure electrical resistance.

On/off Controller: A controller whose action is fully on or fully off.

Open Circuit: The lack of electrical contact in any part of the measuring circuit. An open circuit is usually characterized by rapid large jumps in displayed potential, followed by an off-scale reading.

Operating System: A collection of programs that controls the overall operation of a computer and performs such tasks as assigning places in memory to programs and data, processing interrupts, scheduling jobs and controlling the overall input/output of the system.

Optical Isolation: Two networks which are connected only through an LED transmitter and photoelectric receiver with no electrical continuity between the two networks.

OSHA: Occupational and Safety Hazard Organization.

Output: The electrical signal measured at the output terminals which is produced by an applied input to a transducer.

Output Impedance: The resistance as measured on the output terminals of a pressure transducer at standard temperature, with no measured applied, and with the excitation terminals open-circuited.

Output Noise: The RMS, peak-to-peak (as specified) AC component of a transducer's DC output in the absence of a measurand variation.

Overrange, Safe: The maximum pressure or load which may be applied to the transducer without causing a permanent change in the performance specifications.

Overshoot: The number of degrees that a process exceeds the set point temperature when coming up to the set point temperature.